A human heart has four chambers, the left and right atrium and the left and right ventricles. The chambers of the heart alternately expand and contract to pump blood through the vessels of the body. The cycle of the heart includes the simultaneous contraction of the left and right atria, passing blood from the atria to the left and right ventricles. The left and right ventricles then simultaneously contract forcing blood from the heart and through the vessels of the body. In addition to the four chambers, the heart also includes a check valve at the upstream end of each chamber to ensure that blood flows in the correct direction through the body as the heart chambers expand and contract. These valves may become damaged, or otherwise fail to function properly, resulting in their inability to properly close when the downstream chamber contracts. Failure of the valves to properly close may allow blood to flow backward through the valve resulting in decreased blood flow and lower blood pressure.
Mitral regurgitation occurs when the mitral valve separating the left atrium and the left ventricle fails to properly close. As a result, upon contraction of the left ventricle blood may leak or flow from the left ventricle back into the left atrium, rather than being forced through the aorta.
The mitral valve has 2 leaflets, anterior and posterior, both connected on one side to the mitral annulus and on the free edges to the cordae and cardiac muscle. In order to close properly, the free edges of the two leaflets have to touch each other over a length of several millimeters and this is called leaflets coaptation. Mitral regurgitation is mainly due to a lack of leaflets coaptation as a consequence of annulus dilatation or cardiac muscle dysfunction. Regardless of the cause, mitral regurgitation may result in a decrease in blood flow through the body (cardiac output) and deserve surgical treatment.